The National Transportation Safety Board wrapped up a three-day investigative hearing into the mid-air collision between a helicopter and passenger jet in Washington that killed 67. New information confirms the crew of the Army helicopter faced several problems,

The board focused on air traffic control and heard it was common for pilots to ask to use visual separation — relying on eyesight — just as the Army Black Hawk’s pilot agreed to do the night of the crash.

Incorrect altitude readings on the Army helicopter that collided with a passenger plane over Washington, D.C., in January contributed to the aircraft getting too close, but air traffic controllers warned about the hazards helicopter traffic presented years before the crash.